Integrated circuits dissipate electrical power during operation, transforming electrical energy into heat energy. At the same time, several operating parameters of an integrated circuit typically vary with temperature, and reliable device operation within specifications occurs only within a defined operating temperature range. For high performance devices, such as microprocessors, specified performance is only achieved when the temperature of the device is below a specified maximum operating temperature. Operation of the device at a temperature above the specified maximum operating temperature may result in irreversible damage to the device. In addition, it has been established that the reliability of an integrated circuit decreases with increasing operating temperature.
On-die thermal sensors (also referred to as on-chip thermal sensors) are commonly used to detect the temperature of a portion of a semiconductor chip. For example, one or more digital thermal sensors (DTS) may be integrated into the structure of a chip (e.g., on-die) and used to detect when a particular temperature is reached at that location of the chip. Thermal-related power management decisions are based on the detection of such temperatures. For example, a processor may be designed to throttle back when a temperature of 95° C. is detected, and shut down completely when a temperature of 110° C. is detected. Thus, the on-die DTS is useful for facilitating intelligent decision making of the power-aware architecture to increase performance or throttle voltage.
A DTS is calibrated in order to accurately detect chip temperatures. Calibration of an on-die DTS typically involves subjecting a wafer containing the die to a controlled temperature, connecting the wafer to test equipment, and using a state machine to step through calibration steps to identify a voltage that corresponds to the controlled temperature.
The calibration accuracy of an on-die DTS has a direct influence on guard-bands, affecting bottom line performance in frequency and energy consumption. However, the calibration accuracy of a DTS is typically only to within about +/−5° C. Self-heating of the chip during calibration of the DTS is a particular problem that results when logic on the chip generates heat during the calibration of the DTS and this heat skews the result of the calibration measurement.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.